The invention relates to a method for controlling the triggering of a motor vehicle occupant protection system and a vehicle occupant protection system that is adapted thereto.
Prior-art motor vehicle occupant protection systems are provided with one or more impact sensors whose output signals are evaluated in order to detect an accident, which is critical in terms of safety. Owing to the large number of possible types of accident, the reliable evaluation of the acceleration signals requires a large expenditure. This expenditure is increased even further if vehicle occupant protection components, which fire in multiple stages, for example a multi-stage airbag (with two or more firing caps that are to be fired in succession as a function of the severity of the accident) are to be actuated in a correctly timed way. This also gives rise to stringent hardware requirements in terms of the computing power of the microcontroller or microprocessor used, and these hardware requirements can usually not be met with for an acceptable expense.
In addition, it is difficult to ensure the necessary rapid firing times of the passive restraining systems, i.e. to complete the evaluation calculations within a very short time interval. In addition, in order to improve the vehicle occupant protection system both from the point of view of legislation and also from the point of view of vehicle manufacturers, new test situations for head-on impacts are being defined that require a passive restraining system to be triggered. Currently, customary test situations for head-on impacts are a head-on impact against a rigid wall, an impact against a rigid obstacle with partial covering (offset test), or at an acute angle (angle test), as well as an impact against a deformable obstacle with partial coverage, i.e. an ODB (offset deformable barrier) test.
It is accordingly an object of the invention to provide a method and device for controlling the triggering of a motor vehicle occupant protection system that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that provides a method for controlling the triggering of a motor vehicle occupant protection system that is defined by a good vehicle occupant protection function.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a method for controlling the triggering at least one vehicle occupant protection component of a motor vehicle occupant protection system in the event of an impact. The first step of the method is providing at least one accident sensor and a control unit evaluating the output signals of the accident sensor. The next step is classifying the impact type by the output signal of the accident sensor with an impact type classification section. The next step is including in a triggering algorithm parameters depending on the impact type. The next step is firing the vehicle occupant protection components according to a triggering algorithm.
With the objects of the invention in view, there is also provided a motor vehicle occupant protection system. The motor vehicle occupant protection system includes an accident sensor outputting an output signal and a control unit. The control unit connects to the accident sensor and senses an impact in accordance with a triggering algorithm. The control unit also triggers at least one vehicle occupant protection component in the event of an impact. The triggering algorithm has an accident classification section that determines the type of impact from the output signal. The triggering algorithm is adapted as a function of the determined type of impact.
In accordance with a mode of the invention, in the event of an accident, in addition the type of accident, for example head-on impact against a rigid wall or oblique impact or impact against a deformable obstacle, is sensed. Taking the type of accident into account allows for the signals, which are formed internally for the triggering decision, to be additionally defined as a function of the type of accident, and therefore for a triggering control that is better adapted to the respective accident event to be obtained.
The triggering algorithm is thus adapted as a function of the type of accident detected. This can be accomplished in different ways. It is possible to provide in the control unit different triggering algorithms that are optimized for the individual types of impact. As a function of the type of the impact that is detected, the triggering algorithm that is provided for that type is then called and processed. These triggering algorithms may have a structure that is known per se, for example for the xe2x80x9chead-on impact against a rigid obstaclexe2x80x9d type, in which there is very strong acceleration, the acceleration signal or a variable defined therefrom can simply be compared with a high threshold value. In the case of the xe2x80x9chead-on impact against a deformable obstaclexe2x80x9d impact type, the acceleration signal or a variable defined therefrom can be compared with a lower threshold, and in addition the period for which the acceleration signal exceeds a specific value can also be taken into account.
However, in a preferred embodiment, just one single triggering algorithm is provided. The algorithm is stored in the control unit and its parameters, for example, the level of threshold values, being modified as a function of the type of impact detected. This reduces the requirement of memory space and makes it possible to start processing the triggering algorithm immediately when the start of an impact is detected, even if the detection of the type of impact has not yet been completed.
In a preferred embodiment, the acceleration signal is output by the central acceleration sensor. The central acceleration sensor is generally mounted in the central control unit. The central control unit is normally disposed at the front in the tunnel region. The acceleration signal is utilized and evaluated in two ways, namely on the one hand to detect the type of accident and on the other hand as the acceleration signal that is to be evaluated by the triggering algorithm. Thus, there is no need for an additional, exported sensor. However, if one or more additional exported sensors should be present, their output signal can additionally (or exclusively) be evaluated in order to detect the type of accident and/or during the processing of the triggering algorithm.
If it is not possible to draw unambiguous conclusions about a specific type of accident from the sensor signal profiles, a membership value, in particular, a probability value, which reflects the probability that an accident is of a specific type of accident, is preferably formed. With such an ambiguous assignment, a plurality of probability values may also be obtained, for example 80% for xe2x80x9chead-on impact (0xc2x0) against a rigid obstaclexe2x80x9d and 20% for xe2x80x9cangular head-on impact against a rigid obstaclexe2x80x9d. Such xe2x80x9cfuzzyxe2x80x9d values can be used for xe2x80x9cfuzzyxe2x80x9d influencing of the triggering algorithm, for example for forming weighting factors for evaluating individual variables which are formed and/or evaluated during the processing of the triggering algorithm. The weighting factors, for example, can be set as a function of the probability values to intermediate values between the weighting factors predefined for the individual types of accident.
The invention also can be used advantageously for firing vehicle occupant protection systems, which can be fired in a two-stage or multi-stage fashion, for example two-stage airbags. The type of accident which is detected or the membership value or values determined can then be processed not only in the triggering algorithm section provided for the first firing stage but also in the triggering algorithm section for the second stage, ensuring dual utilization of the sensed type of accident and reliable control of the triggering with acceptable computational outlay and in a sufficiently short time.
The triggering algorithm is advantageously of modular construction: one module performing the detection of the type of accident, while a further module forms comparison values for the comparison with the current acceleration or a variable that is dependent thereon, and a third module carries out the comparison between these variables. This permits already tested triggering algorithms to be used in the second and third modules, which are only additionally influenced by the first module. At the same time, simple and separate parameterization of the modules in adaptation to different types of vehicle, platforms and the like can be completed.
The invention permits not only rough classification of general types of accident such as head-on impact, side collision or rear impact, but is also defined in particular by the possibility of also performing fine classification within the type of accident, namely for example in the case of the xe2x80x9chead-on impactxe2x80x9d type to make a finer distinction between xe2x80x9chead-on impact (angle 0xc2x0) against a rigid obstaclexe2x80x9d, xe2x80x9chead-on impact against a soft obstacle (if appropriate with partial coverage)xe2x80x9d, xe2x80x9chead-on impact with partial coverage against a rigid obstaclexe2x80x9d or xe2x80x9cangular impactxe2x80x9d, and if appropriate the probability of the present impact belonging to the subclasses in question.
The triggering algorithm that is influenced as a function of the type of accident can either be a simple algorithm, in which the acceleration which is currently sensed and is possibly subjected to preprocessing is compared with a threshold value, or can also be a mature algorithm in which variables derived from the acceleration sensor signals are determined and terms are formed which represent specific characteristics such as for example the prediction of the displacement of the head or the like, and are used in defining the variables, for example the threshold values, which are taken into account for the triggering comparison.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and device for controlling the triggering of a motor vehicle occupant protection system, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.